Improvement in screws



LMARSH.

SCREW.

No. 33,487.. Patented Oct. 15, 1861.

Me/55,5 ff

5 Iman/22 Aw' M UNITED STATES PATENT i OFFICE.

LEONARD MARSH, OF BURLINGTON, VERMONT'.

IMPROVEMENT IN SCREWS.

of the same, reference being had to the accompanying drawings, in which- Figure l is a view ot one of my improved.

screws. Fig. 2 showssuch a screw inserted in a matrix C, and Fig. 3 represents a modication of thev invention applicable to screws of thelarger sizes.

The object of the invention is to iix the screw more firmly in its .matrix so that it will not` be aptto turn by the application of a slight force, noir become loose in consequence ot thev wear ot the matrix-a point of im'portance in .many cases in which screws are applied, but of obvious and paramount consequence in many machines and in some instruments of precision, such as those used for mathematical, philosophical,l and astronomical purposes.

The nature of the invention consists in splitting the screw in one or more places in a line parallel to its length, and then imparting "an arched form to the split portion. A screw thus constructed when inserted in a matrix scoinpressed until the flexure of its arched des is overcome; but the elastic reaction of 4the bent metal acts like a wedge to hold the screw fixed, so that no ordiuarymotion, jar,-

or handling will cause itto start back or get loose and so produce derangement or injuryv or interfere with precision and accuracy ot` movement.

In the drawings, Figure l represents a screw A,split up the middle for a part ot` its length, and the split portion l so .bentas to form a double arch. rlhe arched form is imparted by opening the split ends and inserting a rod or mandrel of the proper size andtorni to give the degree of flexure and elasticity required, and bending the'sides over said mandrel until their ends come together, as represented. 'lhe rod is then withdrawn. 'lhe length of the Vslit and the curvature of the a'rch may vary with the size and length of the screw. When the screw is ver f short it may be split nearly the whole length, and in that case the split should be made at right angles to the nick'in the head of the ser-ew.

When the screw is large the slit may be onl one side ot the center, or on both sides, as shown in Fig. 3, and the strips B 1%"arched, as before described.' In this case the arches must be compressed on inserting the screw, so as to make the threads correspond.

Where a very strong` adhesion between the screw and its matrix is required it may be further increased to any degree by inserting iu the slitof the screw a strip of some compressible and elastic substance, as softwood, very narrow, and of a thickness proportioned to the effect desired.

Having thus fully described 'my invention, what I claiimand desire to secure by Letters Patentis- 'lhe method hereinbefore described of increasing' the adhesion between a screw and its matrix by splitting the screw and forming the-split portion into an elastic'arch,sub

. Stantially in the manner and for the purposes set forth.

The above specification signed and wit nessed this 20th day ot` April, A. D. 1861.

LEONARD MARSH'. 

